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1 | Kernel driver lm83 |
2 | ================== | |
3 | ||
4 | Supported chips: | |
5 | * National Semiconductor LM83 | |
6 | Prefix: 'lm83' | |
7 | Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e | |
8 | Datasheet: Publicly available at the National Semiconductor website | |
9 | http://www.national.com/pf/LM/LM83.html | |
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10 | * National Semiconductor LM82 |
11 | Addresses scanned: I2C 0x18 - 0x1a, 0x29 - 0x2b, 0x4c - 0x4e | |
12 | Datasheet: Publicly available at the National Semiconductor website | |
13 | http://www.national.com/pf/LM/LM82.html | |
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14 | |
15 | ||
7c81c60f | 16 | Author: Jean Delvare <jdelvare@suse.de> |
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17 | |
18 | Description | |
19 | ----------- | |
20 | ||
21 | The LM83 is a digital temperature sensor. It senses its own temperature as | |
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22 | well as the temperature of up to three external diodes. The LM82 is |
23 | a stripped down version of the LM83 that only supports one external diode. | |
24 | Both are compatible with many other devices such as the LM84 and all | |
25 | other ADM1021 clones. The main difference between the LM83 and the LM84 | |
26 | in that the later can only sense the temperature of one external diode. | |
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27 | |
28 | Using the adm1021 driver for a LM83 should work, but only two temperatures | |
29 | will be reported instead of four. | |
30 | ||
31 | The LM83 is only found on a handful of motherboards. Both a confirmed | |
32 | list and an unconfirmed list follow. If you can confirm or infirm the | |
33 | fact that any of these motherboards do actually have an LM83, please | |
34 | contact us. Note that the LM90 can easily be misdetected as a LM83. | |
35 | ||
36 | Confirmed motherboards: | |
37 | SBS P014 | |
114cc0c0 | 38 | SBS PSL09 |
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39 | |
40 | Unconfirmed motherboards: | |
41 | Gigabyte GA-8IK1100 | |
42 | Iwill MPX2 | |
43 | Soltek SL-75DRV5 | |
44 | ||
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45 | The LM82 is confirmed to have been found on most AMD Geode reference |
46 | designs and test platforms. | |
47 | ||
be2a608b | 48 | The driver has been successfully tested by Magnus Forsström, who I'd |
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49 | like to thank here. More testers will be of course welcome. |
50 | ||
51 | The fact that the LM83 is only scarcely used can be easily explained. | |
52 | Most motherboards come with more than just temperature sensors for | |
53 | health monitoring. They also have voltage and fan rotation speed | |
54 | sensors. This means that temperature-only chips are usually used as | |
55 | secondary chips coupled with another chip such as an IT8705F or similar | |
56 | chip, which provides more features. Since systems usually need three | |
57 | temperature sensors (motherboard, processor, power supply) and primary | |
58 | chips provide some temperature sensors, the secondary chip, if needed, | |
59 | won't have to handle more than two temperatures. Thus, ADM1021 clones | |
60 | are sufficient, and there is no need for a four temperatures sensor | |
61 | chip such as the LM83. The only case where using an LM83 would make | |
62 | sense is on SMP systems, such as the above-mentioned Iwill MPX2, | |
63 | because you want an additional temperature sensor for each additional | |
64 | CPU. | |
65 | ||
66 | On the SBS P014, this is different, since the LM83 is the only hardware | |
67 | monitoring chipset. One temperature sensor is used for the motherboard | |
68 | (actually measuring the LM83's own temperature), one is used for the | |
69 | CPU. The two other sensors must be used to measure the temperature of | |
70 | two other points of the motherboard. We suspect these points to be the | |
71 | north and south bridges, but this couldn't be confirmed. | |
72 | ||
73 | All temperature values are given in degrees Celsius. Local temperature | |
74 | is given within a range of 0 to +85 degrees. Remote temperatures are | |
75 | given within a range of 0 to +125 degrees. Resolution is 1.0 degree, | |
76 | accuracy is guaranteed to 3.0 degrees (see the datasheet for more | |
77 | details). | |
78 | ||
79 | Each sensor has its own high limit, but the critical limit is common to | |
80 | all four sensors. There is no hysteresis mechanism as found on most | |
81 | recent temperature sensors. | |
82 | ||
83 | The lm83 driver will not update its values more frequently than every | |
84 | other second; reading them more often will do no harm, but will return | |
85 | 'old' values. |